Subsea structures (such as well trees, subsea manifolds and subsea distribution units) in subsea hydrocarbon extraction or injection wells are supplied with at least one of (for example) electric power, hydraulic power, electrical signals, optical signals and chemicals from a control platform or surface vessel via an umbilical, which could be in the form of a hydraulic flying lead (HFL) such as a steel tube flying lead (SFL). The umbilical is typically terminated with a connector which mates with another connector mounted on a stabplate attached to the subsea structure, such as a tree. Stabplate connections are, historically, made up in a horizontal orientation. However, as umbilicals, for example HFLs, become heavier and more unwieldy this leads to designs with the need for increased buoyancy, which increases in-air weight and overall costs.
With such conventional horizontally connected stabplate connections, the installation vessel is typically decoupled from the installation and involves a remotely operated vehicle (ROV) dragging the umbilical across the seabed, which, in some seabed conditions (e.g. Gulf of Mexico, West Africa) leads to a decrease in visibility due to disturbance of sand or silt.
U.S. Pat. Nos. 4,469,136 and 6,481,504 disclose connecting flow lines to an underwater structure by a vertical connection.
Deep Down Inc., of 15473 East Freeway, Channel View, Tex. 77530, USA have disclosed a method of installing an SFL in which the latter is lowered vertically but connected horizontally to a tree using an ROV.
Unitech Offshore AS, of Bergen, Norway N-5004 have produced an ROV installed stabplate connection in which an ROV drops an HFL stabplate on to vertical pins but then mates the stabplate to a structure in a horizontal direction.
OceanWorks International, Inc. of 11611 Tanner Road, Suite A, Houston, Tex. 77041, USA have produced a flying lead connector having a stab connection which can be connected vertically or horizontally using an ROV. See also U.S. Pat. No. 7,172,447.